I have come across with the same issue, with individual files, and this is what I have got with Perl6:

#!/usr/bin/env perl6
use v6;

# Substitute special chars to underscore

my token special_char { <[ \s \( \) ]> };

multi MAIN( 
        Str $filename where ( 
            $filename.IO ~~ :f  and $filename.match( &special_char ) 
        )
    ) 
{
    $filename.IO.rename( $filename.subst( /<special_char>/ , '_', :g) 
+);
}

multi MAIN( 
    Str $filename where ( $filename.IO ~~ :f  and ! $filename.match( &
+special_char) )
    ) { 
    say "File '$filename' has no spepcial characters"; 
}

multi MAIN( Str $filename where !($filename.IO ~~ :f) ) { 
    say "File '$filename' does not exist";
}

sub USAGE() { 
    say "Usage: NoSpace file-name"; 
}
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